Conventional photolithography technology used during semiconductor fabrication includes a double patterning technology by ArF liquid immersion exposure, EUV lithography and nanoimprint lithography. Conventional photolithography technology, however, has some drawbacks, such as higher production costs, a decrease in throughput, continued further miniaturization of the pattern, among other challenges.
Under such a situation, it is expected that directed self-assembly (DSA) may be applied to lithography technology. DSA can form a pattern having higher dimensional accuracy because it occurs by a spontaneous action of energy stabilization. Additionally, the technology utilizing microphase separation of a high-molecular block copolymer can form a periodic structure having various shapes, ranging in size from several nanometers to several hundred nanometers, by implementation of simple coating and annealing. Spherical, cylindrical, or lamella-shaped formations can be obtained by altering the composition ratio of the high-molecular block copolymer; and various sizes of a dot pattern, a hole or pillar pattern, or a line pattern, and so on, can be formed by altering those sizes according to molecular weight.
A form, within which, the polymer phase formed by self-assembly occurs, is required for a broad and intended formation using DSA. As a form, a physical guide (grapho-epitaxy), which facilitates a microphase separation pattern at a depressed region of a pattern having projected portions adjacent the depressed regions, and a chemical guide (chemical-epitaxy), which controls the forming position of microphase separation based on the difference in surface energy underneath the DSA material, are known.
When forming a microphase separation by using such a guide and coating a self-assembly material on a base coating having adjusted interfacial energy, the self-assembly material is phase separated periodically (regularly) due to the effect of interfacial energy near the base coating; alternately, the self-assembly material is not phase separated periodically (regularly) because there is minimal effect of interfacial energy around the area spaced-away from the base coating. This is because periodical phase separation is in a metastable state and the self-assembly material will perform random phase separation that is at its most stable state without additional energy from outside. Therefore, conventionally, the thickness of the self-assembly material is decreased so that the effect of interfacial energy of the base coating is realized entirely when forming a periodical microphase separation pattern. However, the problem of a microphase separation pattern having such small thickness is that it lacked sufficient robustness of fabrication.